1. Field of the Invention
The present invention relates to operator interfacing methods for inputting operator-selectable control parameters to a centrifuge instrument.
2. Description of the Prior Art
A centrifuge instrument is a device operable to expose a liquid sample carried within a centrifuge rotor to a centrifugal force field. The rotor is mounted on the upper end of a drive spindle that projects into an enclosed chamber. Typically, a cooling arrangement is provided whereby the temperature of the sample may be controlled for the centrifuge run.
The most common operator-selectable control parameters of a centrifuge run are: (1) rotor angular velocity ("speed") and its associated parameter (2) relative centrifugal force ("RCF"), (3) sample temperature, and (4) duration of the run. The unit for relative centrifugal force is ("xG"), where G is force due to gravity.
For instruments operating in the so-called "ultra-speed" regime it is common that the angular velocity needed to perform a selected protocol may lie in the range from approximately twenty thousand through approximately eighty to one hundred thousand revolutions-per-minute (rpm). The value of relative centrifugal force to which a sample is exposed during a run is dependent both upon the rotor speed and the distance of the sample from the axis of rotation. Values of this parameter in excess of one hundred thousand xG are common.
For the large majority of protocols (on the order of seventy-five percent) a sample temperature of four degrees (4.degree. C.) is used. A lesser but still significant number of protocols (on the order of an additional fifteen percent) require a sample of temperature twenty degrees (20.degree. C.). The remainder of protocols may require an alternative temperature value between 0.degree. C. and 40.degree. C.
The time duration for a centrifuge run is either implemented using an "elapsed time" mode or an indefinite time ("HOLD") mode. In the former the centrifuge run extends for a time period selected by the operator. The run is automatically terminated at the end of that period. In the latter mode the centrifuge run continues until it is manually terminated by the operator.
Most operator manipulable control panels for centrifuge instruments include a speed parameter function control key, a temperature parameter function control key, a time parameter function control key, and a time "HOLD" parameter function control key. The numeric values for the selected speed parameter, temperature parameter and time parameter are input to the instrument using a ten-digit (zero through nine) control pad. The indefinite time mode is input using the separate "HOLD" function control key. The operator's choices of settings for the various parameters are displayed in respective display fields provided on a visual display. An "ENTER" key transmits a command to the microprocessor-based instrument controller. A "START" key is normally used to execute a run having the selected parameter settings.
Presently, in instruments such as the RC-28S Supraspeed.TM. instrument manufactured and sold by Biotechnology Systems Division of E. I. duPont de Nemours the set value of the speed parameter is input serially, with the entry of each digit shifting the previously-entered digit(s) to the left by one place. All of the digits must be entered, even if the set value is an even multiple of either one hundred or one thousand.
Efforts have been made to simplify the inputting of the various operator-selectable control parameters to the controller.
For example, in the case of selection of rotational speed, an operator interface is used on instruments manufactured by Beckman Instruments and sold as Optima.TM. Series preparative ultracentrifuge. With this interfacing technique, it is presumed that the desired speed parameter is an even multiple of one-hundred, and that regulation of the speed parameter to a resolution finer than one hundred rpm is not desired. Upon entry, each digit of the speed parameter value is initially displayed in the hundred's place on the display field. Prior significant digits are shifted to the left upon the entry of each successive digit.
A variation of the above-described interfacing technique when rotational speed is entered is practiced in the instrument sold by Biotechnology Systems Division of E. I. duPont de Nemours as the RC-M-120 micro-ultracentrifuge. With this interfacing technique it is presumed that the desired speed parameter is an even multiple of one-thousand. Upon entry each digit of the speed parameter value is initially displayed in the thousand's place on the display field. Earlier entered significant digits are shifted to the left upon the entry of each successive digit.
In both of the above-referenced instruments the entry of the time parameter value is set using either the time function control key (followed by the entry of the digits of the desired time value if a predetermined elapsed time value is desired), or, after depressing the time function control key, using the separate "HOLD" function control key (if the indefinite time mode is desired).
In the same instruments the temperature set value is input using the temperature parameter function control key, with the desired temperature value being serially entered.